sec-gdkevent.html

gtk 开发手册和参考文档。 包括gtk glib gdk等

            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">
                GDK_KEY_RELEASE_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_KEY_RELEASE</span>
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">
                GDK_ENTER_NOTIFY_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_ENTER_NOTIFY</span>
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">
                GDK_LEAVE_NOTIFY_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_LEAVE_NOTIFY</span>
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">
                GDK_FOCUS_CHANGE_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_FOCUS_IN</span>, <span
                class="STRUCTNAME">GDK_FOCUS_OUT</span>
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_STRUCTURE_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_CONFIGURE</span>,
                <span class="STRUCTNAME">GDK_DESTROY</span>, <span
                class="STRUCTNAME">GDK_MAP</span>, <span class= 
                "STRUCTNAME">GDK_UNMAP</span>
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">
                GDK_PROPERTY_CHANGE_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_PROPERTY_NOTIFY</span>
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">
                GDK_VISIBILITY_NOTIFY_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">
                GDK_VISIBILITY_NOTIFY</span>
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">
                GDK_PROXIMITY_IN_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_PROXIMITY_IN</span>
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">
                GDK_PROXIMITY_OUT_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_PROXIMITY_OUT</span>
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">
                GDK_SUBSTRUCTURE_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                Receive <span class="STRUCTNAME">
                GDK_STRUCTURE_MASK</span> events for <i class= 
                "EMPHASIS">child windows</i>
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_ALL_EVENTS_MASK</span>
              </td>
              <td align="LEFT" valign="TOP">
                All events
              </td>
            </tr>
          </table>
        </div>
      </div>
      <div class="SECT2">
        <h2 class="SECT2">
          <a name="SEC-GTKEVENTS">Receiving GDK Events in GTK+</a>
        </h2>
        <p>
          In a GTK+ program, you will never receive GDK events
          directly. Instead, all events are passed to a <tt class= 
          "CLASSNAME">GtkWidget</tt>, which emits a corresponding
          signal. You handle events by connecting handlers to <tt
          class="CLASSNAME">GtkWidget</tt> signals.
        </p>
        <p>
          The X server sends each X client a stream of events.
          Events are sent and received in the order of their
          occurrence. GDK converts each <span class="STRUCTNAME">
          XEvent</span> it receives into a <span class=
          "STRUCTNAME">GdkEvent</span>, then places events in a
          queue. GTK+ monitors GDK's event queue; for each event
          received, it decides which widget (if any) should receive
          the event. The <tt class="CLASSNAME">GtkWidget</tt> base
          class defines signals for most event types (such as <span
          class="SYMBOL">"button_press_event"</span>); it also
          defines a generic <span class="SYMBOL">"event"</span>
          signal. The GTK+ main loop calls <tt class="FUNCTION">
          gtk_widget_event()</tt> to deliver an event to a widget;
          this function first emits the <span class="SYMBOL">
          "event"</span> signal, then emits a signal for the
          specific event type (if appropriate). Some events are
          handled in special ways; notably, drag-and-drop events do
          not directly correspond to drag-and-drop signals.
        </p>
        <p>
          In general, events go to the widget owning the <span
          class="STRUCTNAME">GdkWindow</span> the event occurred
          on. However, there are certain special cases.
        </p>
        <p>
          if a widget has the grab (i.e., if <tt class="FUNCTION">
          gtk_grab_add()</tt> was called, see <a href= 
          "z57.html#SEC-GRABS">the section called <i>Grabs</i> in
          the chapter called <i>GTK+ Basics</i></a>), certain
          events will only be forwarded to the widget with the
          grab, or the children of that widget. Events that occur
          on other widgets are ignored. Only certain user-initiated
          events such as button events and key events are affected
          by a grab.
        </p>
        <p>
          Widget sensitivity (see <a href=
          "z57.html#SEC-SENSITIVITY">the section called <i>
          Sensitivity</i> in the chapter called <i>GTK+
          Basics</i></a>) also affects where events are sent.
          Events representing user interaction are not forwarded to
          insensitive widgets.
        </p>
        <p>
          As you might expect, widgets with no associated <span
          class="STRUCTNAME">GdkWindow</span> do not originate
          events; X only sends events to windows. There is one
          exception: containers synthesize expose events for their
          windowless children.
        </p>
        <p>
          The GTK+ main loop <i class="EMPHASIS">propagates</i>
          certain events from child widgets to their parent
          containers. That is, for each event, a signal is emitted
          first from a child widget, then from its immediate
          parent, then from the parent's parent, and so on. For
          example, if you click a <tt class="CLASSNAME">
          GtkMenuItem</tt>, it ignores the button press and lets
          the menu it's a part of handle it. Some events are not
          propagated; <a href="sec-gdkevent.html#TAB-WIDGETEVENTS">
          Table 4</a> gives details.
        </p>
        <p>
          Event propagation ends once a widget "handles" the event.
          This ensures that only one user-visible change results
          from any user action. Handlers for <tt class="CLASSNAME">
          GtkWidget</tt>'s event signals must return a <span class= 
          "STRUCTNAME">gint</span> value. Recall that the last
          signal handler to run determines the return value of a
          signal emission---see <a href="z109.html#SEC-EMITTING">
          the section called <i>Emitting A Signal</i> in the
          chapter called <i>The GTK+ Object and Type
          System</i></a>. All event signals are <span class= 
          "STRUCTNAME">GTK_RUN_LAST</span>, so the return value
          will come from:
        </p>
        <ul>
          <li>
            <p>
              The last handler connected with <tt class="FUNCTION">
              gtk_signal_connect_after()</tt>, if any.&#13;
            </p>
          </li>
          <li>
            <p>
              Otherwise, the widget's default signal handler, if
              any.&#13;
            </p>
          </li>
          <li>
            <p>
              Otherwise, the last handler connected with <tt class= 
              "FUNCTION">gtk_signal_connect()</tt>, if any.&#13;
            </p>
          </li>
          <li>
            <p>
              Otherwise, the default return value is <span class= 
              "STRUCTNAME">FALSE</span>.&#13;
            </p>
          </li>
        </ul>
        <p>
          If the emission of an event signal returns <span class= 
          "STRUCTNAME">TRUE</span>, the GTK+ main loop will stop
          propagating the current event. If it returns <span class= 
          "STRUCTNAME">FALSE</span>, the main loop will propagate
          the event to the widget's parent. Recall that each event
          results in two signal emissions: a generic <span class= 
          "SYMBOL">"event"</span> signal and a specific signal
          (such as <span class="SYMBOL">"button_press_event"</span>
          or <span class="SYMBOL">"key_press_event"</span>). If <i
          class="EMPHASIS">either</i> emission returns <span class= 
          "STRUCTNAME">TRUE</span>, event propagation ends. The
          return value from the generic <span class="SYMBOL">
          "event"</span> signal has one additional effect: if <span
          class="STRUCTNAME">TRUE</span>, the second, more specific
          signal will not be emitted.
        </p>
        <p>
          <a href="sec-gdkevent.html#TAB-WIDGETEVENTS">Table 4</a>
          summarizes how <tt class="CLASSNAME">GtkWidget</tt>
          signals correspond to event types, which events are
          affected by an active grab, and which events are
          propagated from parent to child. Signal handlers for all
          event signals should return a <span class="STRUCTNAME">
          gint</span> and take three arguments: the widget emitting
          the signal, the event which triggered the signal, and a
          user data pointer.
        </p>
        <div class="TABLE">
          <a name="TAB-WIDGETEVENTS"></a>
          <p>
            <b>Table 4. <tt class="CLASSNAME">GtkWidget</tt>
            Events</b>
          </p>
          <table border="1" bgcolor="#E0E0E0" cellspacing="0"
          cellpadding="4" class="CALSTABLE">
            <tr>
              <th align="LEFT" valign="TOP">
                Event Type
              </th>
              <th align="LEFT" valign="TOP">
                <tt class="CLASSNAME">GtkWidget</tt> Signal
              </th>
              <th align="LEFT" valign="TOP">
                Propagated?
              </th>
              <th align="LEFT" valign="TOP">
                Grabbed?
              </th>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_DELETE</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="SYMBOL">"delete_event"</span>
              </td>
              <td align="LEFT" valign="TOP">
                No
              </td>
              <td align="LEFT" valign="TOP">
                No
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_DESTROY</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="SYMBOL">"destroy_event"</span>
              </td>
              <td align="LEFT" valign="TOP">
                No
              </td>
              <td align="LEFT" valign="TOP">
                No
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_EXPOSE</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="SYMBOL">"expose_event"</span>
              </td>
              <td align="LEFT" valign="TOP">
                No
              </td>
              <td align="LEFT" valign="TOP">
                No
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_MOTION_NOTIFY</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="SYMBOL">"motion_notify_event"</span>
              </td>
              <td align="LEFT" valign="TOP">
                Yes
              </td>
              <td align="LEFT" valign="TOP">
                Yes
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_BUTTON_PRESS</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="SYMBOL">"button_press_event"</span>
              </td>
              <td align="LEFT" valign="TOP">
                Yes
              </td>
              <td align="LEFT" valign="TOP">
                Yes
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_2BUTTON_PRESS</span>
              </td>
              <td align="LEFT" valign="TOP">
                <span class="SYMBOL">"button_press_event"</span>
              </td>
              <td align="LEFT" valign="TOP">
                Yes
              </td>
              <td align="LEFT" valign="TOP">
                Yes
              </td>
            </tr>
            <tr>
              <td align="LEFT" valign="TOP">
                <span class="STRUCTNAME">GDK_3BUTTON_PRESS</span>